The present invention relates to a novel process of preparing a 2-methyl-3-aminobenzotrifluoride (MA-BTF) which is useful as an intermediate of some medicines, agricultural chemicals and other chemical products. For example, U.S. Pat. Nos. 3,891,761 and 3,839,344 disclose the N-methyl-D-glucamine salt of 2-(2'-methyl-3'-trifluoromethylanilino) nicotinic acid which is derived from MA-BTF and particularly suitable as a parenterally administered analgesic agent.
There have been some proposals of process for preparing MA-BTF. For example, U.S. Pat. No. 4,209,464 discloses a process of preparing MA-BTF from 3-amino-4-chlorobenzotrifluoride. In this method, at first, 3-amino-4-chlorobenzotrifluoride is reacted with dimethylsulfoxide in the presence of phosphorus pentoxide and triethylamine to produce N-(2-chloro-5-trifluoromethyl) phenyl-S,S-dimethylsulfimide. Then, the dimethylsulfimide is converted to 3-amino-4-chloro-2-methylthiomethylbenzotrifluoride by a chemical rearrangement. Then, this trifluoride is reduced with Raney nickel to form MA-BTF. However, in this process, due to the use of a large amount of phosphorus pentoxide, there are some problems in the recovery method and the processing method of the product. Therefore, this process is not suitable for operation in an industrial scale.
GB-B-2194533 discloses another process of preparing MA-BTF. In this process, at first, 3,4-dichlorotoluene is converted to 2-methyl-4,5-dichlorobenzotrichloride by carbon tetrachloride in the presence of aluminum chloride. Then, this trichloride is fluorinated to form 2-methyl-4,5-dichlorobenzotrifluoride. Then, this trifluoride is nitrated to form 2-methyl-3-nitro-4,5-dichlorobenzotrifluoride. Then, this trifluoride is hydrogenated to form MA-BTF. However, this process is not recommendable from an environmental point of view because carbon tetrachloride which is considered to destroy the ozone layer of the earth is used as a raw material.